Method and apparatus for aligning a waveguide with a radiation source

ABSTRACT

A method and apparatus for aligning an optical waveguide with a radiation source are provided. The waveguide has a longitudinal axis that defines a main optical propagation path. The optical waveguide is illuminated by the radiation source such that the waveguide generates light via photoluminescence, at least a portion of the light generated via photoluminescence being emitted from the waveguide along a direction generally transverse to the longitudinal axis. An output signal is generated at least in part on the basis of light emitted from the waveguide along a direction generally transverse to the longitudinal axis. The alignment of the radiation source and the waveguide is varied at least partly in dependence of the output signal.

FIELD OF THE INVENTION

[0001] This invention relates a method and an apparatus for aligning awaveguide with a radiation source, and more particularly, to a method anapparatus for aligning a waveguide with a radiation source usingphotoluminescence induced in the waveguide by the radiation source.

BACKGROUND

[0002] Many processes involving optical waveguides require a precisealignment between an optical waveguide and a radiation beam. Forexample, in Bragg grating writing by flood exposure, an ultraviolet (UV)laser light interference pattern is used to write the grating in a coreof an optical fiber. The interference pattern, which is typicallyfocussed, needs to be precisely aligned with the core. If the corereceives light from a part of the interference pattern outside of thefocus, the intensity of the interference pattern will not be maximal andan exposure time to the beam required to write a given Bragg gratingwill be increased with respect to the exposure time that would berequired if the core was at the focus of the interference pattern. Inaddition, if no monitoring of the Bragg grating writing process can beperformed during the writing phase, the absence of a well-controlledinterference pattern intensity may lead to a Bragg grating into whichindex of refraction variations are not large enough to provide arequired grating performance.

[0003] The photoluminescence of several materials used to manufactureoptical fibers and other optical waveguides can be used to align theoptical fiber with a laser beam in preparation for Bragg gratingwriting. Once the optical fiber is properly aligned, the laser beam isreplaced by the interference pattern and the Bragg grating writingprocess can be performed.

[0004] Typically, an ultraviolet (UV) laser is held immobile andproduces the laser beam. A supporting member supports the optical fiber,the longitudinal axis of the optical fiber being perpendicular to thelongitudinal axis of the laser beam. The supporting member is mobile ina direction perpendicular to the longitudinal axis of the optical fiberand perpendicular to the longitudinal axis of the laser beam. Thesupporting member can be displaced either manually or with a motorizedactuator.

[0005] When a portion of the laser beam illuminates the photoluminescentcore of the optical fiber, the light produced by photoluminescence ispropagated through the optical fiber to its extremities. A power meterlocated at one extremity of the fiber can then measure the intensity ofthe photoluminescence light, which depends on the power carried by theportion of the laser beam illuminating the core of the optical fiber.Accordingly, when the focus of the laser beam is centered on the core ofthe optical fiber, the intensity of the photoluminescence measured atthe power meter is maximal. Therefore, to center the optical fiber onthe laser beam, the supporting member is displaced to achieve a maximalvalue of the intensity of the photoluminescence detected at theextremity of the optical fiber.

[0006] The method described above requires that the power meter blockone extremity of the optical fiber. In some instances, this isundesirable as it could be advantageous to have other equipment, such asBragg grating writing monitoring equipment, connected to the extremitiesof the optical fiber.

[0007] Against this background, there exists a need to provide novelmethods and devices for aligning a waveguide with a radiation source.

SUMMARY

[0008] In accordance with a broad aspect, the invention provides andapparatus for aligning an optical waveguide with a radiation source. Thewaveguide has a longitudinal axis that defines a main opticalpropagation path and the radiation source illuminates the waveguide suchthat the waveguide generates light via photoluminescence. At least aportion of the light generated via photoluminescence is emitted from thewaveguide along a direction generally transverse to the longitudinalaxis. The apparatus includes a sensor responsive to the light emittedfrom the waveguide along a direction generally transverse to thelongitudinal axis for producing an output signal. Alignment means thenvary the alignment of the radiation source and the waveguide at leastpartly in dependence of the output signal.

[0009] Advantageously, the invention allows aligning an opticalwaveguide with a radiation source, such as a laser, by using lightgenerated through photoluminescence and emitted along a directiongenerally transverse to the longitudinal axis of the waveguide. By usingphotoluminescence emitted transversely to the longitudinal axis of thewaveguide rather than detecting photoluminescence emitted at anextremity of the optical waveguide, the extremities of the opticalwaveguide remain free and can therefore by used for other usefulpurposes such as signal analysis.

[0010] In a specific example of implementation, the output signalgenerated by the sensor is an intensity signal indicative of anintensity of light. In a specific example of implementation, thealignment means includes a controller module responsive to the intensitysignal for causing the alignment of the radiation source and thewaveguide to be varied.

[0011] In a first non-limiting implementation, the controller modulecauses the waveguide to be displaced in order to cause the alignment ofthe radiation source and the waveguide to be varied.

[0012] In a second non-limiting implementation, the controller modulecauses the radiation source to be displaced in order to cause thealignment of the radiation source and the waveguide to be varied.

[0013] In a non-limiting implementation, the alignment means furthercomprise a light reflecting member positioned such as to redirect aradiation beam emitted by the radiation source. The reflecting membermay be any suitable component adapted to reflect a radiation beam. Aspecific example of a light reflecting member is a mirror. In a specificnon-limiting implementation, the light reflecting member is in the formof a mirror. The controller module is operative to cause the lightreflecting member to be displaced in, order to cause the alignment ofthe radiation source and the waveguide to be varied.

[0014] The controller module generates a control signal at least in parton the basis of the intensity signal. An actuator, responsive to thecontrol signal generated by the controller module, displaces the lightreflecting member such as to vary the alignment of the radiation sourceand the waveguide at least in part on the basis of the control signal.The displacing of the light reflecting member may be effected by meansof rotation, by means of translation or by a combination of thetranslation and rotation of the light reflecting member.

[0015] In accordance with another broad aspect, the invention provides amethod for aligning an optical waveguide with a radiation source, thewaveguide having a longitudinal axis that defines a main opticalpropagation path. The method includes illuminating the waveguide suchthat the waveguide generates light via photoluminescence, at least aportion of the light generated via photoluminescence being emitted fromthe waveguide along a direction generally transverse to the longitudinalaxis. An output signal is generated at least in- part on the basis oflight emitted from the waveguide along a direction generally transverseto the longitudinal axis. The alignment of the radiation source and thewaveguide is then varied at least partly in dependence of the outputsignal.

[0016] In accordance with another broad aspect, the invention providesan apparatus for aligning an optical waveguide with a radiation source.The apparatus includes a waveguide support member, a sensor and acontroller module. The waveguide support member is for holding anoptical waveguide, the waveguide having a longitudinal axis that definesa main optical propagation path. The radiation source illuminates thewaveguide such that the waveguide generates light via photoluminescence,at least a portion of the light generated via photoluminescence beingemitted from the waveguide along a direction generally transverse to thelongitudinal axis. The sensor is positioned in proximity to the opticalwaveguide and is responsive to the light emitted from the waveguidealong a direction generally transverse to the longitudinal axis toproduce an intensity signal indicative of a measure of the lightdetected. The controller module is responsive to the intensity signalfor causing the alignment of the radiation source and the waveguide tobe varied at least partly in dependence of the intensity signal.

[0017] In a first specific example of implementation, the waveguidesupport member is moveable and the controller module is responsive tothe intensity signal for causing the waveguide support member to bedisplaced such as to cause the alignment of the radiation source and thewaveguide to be varied.

[0018] In a first specific example of implementation, the controllermodule is responsive to the intensity signal for causing the directionof the radiation beam emitted by the radiation source to be altered suchthat the alignment of the radiation source and the waveguide to bevaried.

[0019] Other aspects and features of the present invention will becomeapparent to those ordinarily skilled in the art upon review of thefollowing description of specific embodiments of the invention inconjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A detailed description of examples of implementation of thepresent invention is provided herein below with reference to thefollowing drawings, in which:

[0021]FIG. 1 shows an apparatus for aligning a laser beam with anoptical fiber in accordance with a specific example of implementation ofthe invention;

[0022]FIG. 2 shows an enlarged view of a portion of the apparatus ofFIG. 1;

[0023]FIG. 3a shows a light reflecting member in the form of a mirrorposition to reflect a radiation beam in a first direction in accordancewith a specific example of implementation of the invention;

[0024]FIG. 3b shows a light reflecting member in the form of a mirrorposition to reflect a radiation beam in a second direction in accordancewith a specific example of implementation of the invention;

[0025]FIG. 3c shows a light reflecting member in the form of a mirrorposition to reflect a radiation beam in a third direction in accordancewith a specific example of implementation of the invention.

[0026] In the drawings, embodiments of the invention are illustrated byway of example. It is to be expressly understood that the descriptionand drawings are only for the purposes of illustration and as an aid tounderstanding, and are not intended to be a definition of the limits ofthe invention.

DESCRIPTION OF THE INVENTION

[0027]FIG. 1 shows an apparatus 100 for aligning an optical waveguide inthe form of an optical fiber 110 with a radiation beam 120. While anoptical fiber 110 is aligned with a radiation beam 120 in the apparatus100, a similar apparatus could be used to align any other type ofwaveguide, such as optical fibers pre-assembled on a module orwaveguides manufactured through integrated optics processes, with aradiation beam.

[0028] The apparatus 100 includes a waveguide support member in the formof a fiber support 130, an actuator 140, a controller 150, a mirror 160mounted on an axle 155, a laser 170 and a sensor 180. In operation, thelaser 170 emits the radiation beam 120 towards the mirror 160. Themirror 160 redirects the radiation beam 120 in the general direction ofthe optical fiber 110, which is held by the fiber support 130. Duringthe alignment procedure, the actuator 140 rotates the mirror 160 throughthe axle 155 and under the control of the controller 150, therebychanging the direction of the radiation beam 120 reflected by the mirror160.

[0029] When the mirror 160 is oriented such that the beam 120illuminates the optical fiber 110, the optical fiber 110 emitsphotoluminescence in the form of visible light, which is propagatedthrough the optical fiber 110. The sensor 180 then detects the visiblelight propagated in the optical fiber 110 at a location remote from thepoint at which the beam 120 intersects the optical fiber 110. As shownon FIG. 1, the sensor 180 detects visible light emitted radially fromthe optical fiber 110. The sensor 180 then produces an intensity signalrelated to an intensity of the light propagated by the optical fiber110. The intensity signal is fed to the controller 150, which uses theintensity signal to control the actuator 140 in order to align theradiation beam 120 with the optical fiber 110.

[0030] As shown on FIG. 2, the optical fiber 110 includes a core 205, acladding 210 and, optionally, a coating 215. The core 205 includes aphotoluminescent material. In the specific example of implementationpresented on FIGS. 1 and 2, the core emits visible light whenilluminated with UV radiation. However, the reader skilled in the artwill readily appreciate that a core 205 having any other type ofphotoluminescence properties can be used without detracting from thespirit of the invention. Typically, the photoluminescence of the core205 shows a reduction in intensity as a function of time when the UVradiation illuminates steadily the core 205. The cladding 210 iscomposed of a material having optical properties suitable for allowingthe propagation of light in the core 205 through total internalreflection. The optional coating 215 protects the cladding 210. Suchcoatings 215 are well known in the art and will not be described infurther details. In the specific example of implementation shown onFIGS. 1 and 2, the coating 215 is opaque to UV radiation and a portionof the coating 215 is removed from the optical fiber 110 prior to thealignment process. It will be appreciated that if an UV transparentcoating 215 is used, removal of the portion of the coating 215 may beomitted.

[0031] Only a small portion of the optical fiber 110 is shown on FIGS. 1and 2. The person skilled in the art will appreciate that the alignmentof the optical fiber 110 with the radiation beam 120 can be performed asdescribed herein irrespective of the total length of the optical fiber110.

[0032] When the radiation beam 120 illuminates the core 205,photoluminescence is produced and the visible light thereby generated ispropagated through the optical fiber 110. A portion of the visible lightis emitted radially from the optical fiber 110 at a location remote fromthe point at which it is produced.

[0033] The fiber support 130 holds a portion of the optical fiber 110which is to be aligned with the radiation beam 120. The exact shape andmaterial of the fiber support 130 are not critical to the presentinvention. In a specific example of implementation, the fiber support130 is immobile. In another specific example of implementation, thefiber support can be displaced manually to facilitate the access to theoptical fiber 110. In a further specific example of implementation, thefiber support 130 is mounted on a mobile platform which allows a coarsealignment of the optical fiber 110 with the radiation beam 120.

[0034] The laser 170 produces the radiation beam 120. While a laser 170producing an UV radiation beam 120 is used in the specific example ofimplementation shown on FIGS. 1 and 2, the reader skilled in the artwill readily appreciate that any other suitable source of radiationcould be used with the present invention as long as it has thecapability to produce a radiation beam 120 that causes photoluminescencein the optical fiber 110. In a specific example of implementation, thelaser 170 includes optical components for focussing and collimating theradiation beam 120.

[0035] The radiation beam 120 coming from the laser 170 is redirected inthe general direction of the optical fiber 110 by the mirror 160. Themirror 160 is mounted on the axle 155 which allows the mirror 160 torotate around the axis of the axle 155. In the specific example ofimplementation shown on FIG. 1, the radiation beam 120 exits the laser170 in a direction generally parallel with the optical fiber 110. Themirror 160 is mounted at a 45 degrees angle with respect to the opticalfiber 110. The axis of the axle 155 is also substantially parallel tothe optical fiber 110. The mirror 160 is adapted to sweep the radiationbeam 120 in a plane generally perpendicular to the optical fiber 110.The skilled person in the art will appreciate that the radiation beam120 may exit the laser 170 in any suitable direction and does not needto be parallel with the optical fiber 110. In such a case, the mirror160 is mounted at an angle that allows the mirror to sweep the radiationbeam 120 originating from the laser 170 in a plane generallyperpendicular to the optical fiber 110.

[0036] The actuator 140, which is controlled by the controller 150,rotates the mirror 160 around the axis of the axle 155. The method usedby the controller 150 to control the rotation of the mirror 160 isdescribed in further details below.

[0037] The rotation of the mirror 160 changes an amount of power carriedby the radiation beam 120 to the core 205. Therefore, thephotoluminescence produced in the core 205 varies in intensity. Thesensor 180 measures the intensity of the photoluminescent visible lightwhich exits the optical fiber 110 radially. The sensor 180 is located ata position remote from the location at which the radiation beam 120induces the photoluminescence. In a specific example of implementation,the sensor 180 is located approximately 2 cm from the source of thephotoluminescence and within 50 to 200 micrometers from the surface ofthe optical fiber 110. However, depending on the exact type of sensor180 used in the apparatus 100, the sensor 180 could be located within afew millimeters of the source of the photoluminescence or a fewkilometers away from the source of the photoluminescence withoutdetracting from the spirit of the invention. Preferably, the sensor 180is affixed to the apparatus 100 so that the position of the sensor 180relatively to the optical fiber 110 does not vary while the alignmentmethod is performed.

[0038] In a specific example of implementation, the coating 215 of theoptical fiber is removed form the fiber at the location at which thesensor 180 is located. Alternatively, if the coating is transparent tothe visible light emitted by photoluminescence, the sensor 180 can belocated at location wherein the coating 215 is intact. In thisalternative, the sensor can be in contact with the coating 215.

[0039] In a variant not shown in the drawings, the sensor 180 includes amultimode optical fiber connected to a remote power meter. The multimodeoptical fiber collects a portion of the photoluminescence visible lightemitted radially from the optical fiber 110 and carries this portion ofthe visible light to the remote power meter, which generates ameasurement of the intensity of the visible light.

[0040] The sensor 180 issues an intensity signal to the controller 150through a sensor output 182. The intensity signal includes informationregarding the intensity of the visible light received by the sensor 180.The controller 150 receives the intensity signal at a controller input152 and is adapted to store corresponding intensity values in a memory.

[0041] In addition, the controller 150 is operative to issue controlsignals to an actuator input 142 of the actuator 140 through acontroller output 154. The control signals instruct the actuator 140 torotate the mirror 160 at a desired angle through the axle 155. In aspecific example of implementation, the controller 150 is adapted toangle the mirror 160 at an angle that maximizes the power of theradiation beam 120 illuminating the core 205. As the reader skilled inthe art will appreciate, other alignment criteria are possible withoutdetracting form the spirit of the invention.

[0042] In a specific example of implementation, the alignment of theradiation beam 120 with the optical fiber 110 is performed in accordancewith the following method. First, the optical fiber is coarsely alignedwith the radiation beam while the mirror 160 is kept immobile. Then, thecontroller 150 sends control signals instructing the actuator 140 torotate the mirror 160 in an oscillating manner while storing in thememory the intensity signals from the sensor 180. A value of an angle atwhich the mirror 160 is positioned is stored in the memory each time anintensity value is stored. After a predetermined number of oscillations,the controller 150 uses the intensity values and the mirror angle valuesstored in the memory to determine an optimal angle that the mirror 160should assume so that the radiation beam 120 illuminates the opticalfiber 110 in an optimal manner. As mentioned previously, in a specificexample of implementation, the illumination is optimal when theintensity of the photoluminescence produced by the radiation beam 120 ismaximal. If the radiation beam 120 is focussed, this corresponds tohaving the focal region of the radiation beam centered on the core 205.

[0043] For the purpose of illustration only, FIG. 3a shows a simplifieddiagram of the mirror 160 rotated to direct a radiation beam in a firstdirection such that the beam illuminates a first portion of thewaveguide. FIG. 3b shows a simplified diagram of the mirror 160 rotatedto direct a radiation beam in a second direction such that the beamilluminates a second portion of the waveguide. FIG. 3c shows asimplified diagram of the mirror 160 rotated to direct a radiation beamin a third direction such that the beam illuminates a third portion ofthe waveguide. In a non-limiting implementation, FIG. 3c shows thetilting mirror at an optimized position for alignment.

[0044] The coarse alignment of the optical fiber with the radiation beamis the first step performed. During this coarse alignment, the mirror160 is kept immobile and the fiber support 130 is displaced. Asmentioned previously, the coarse alignment is optional and can either beperformed manually by an operator or automatically, for example usingcameras and image processing software. The coarse alignment serves tolocate the optical fiber 110 within a range of positions accessible bythe radiation beam 120 under the rotation of the mirror 160.

[0045] After the coarse alignment is performed, the angle of the mirroraround the axle 155 is changed in an oscillating manner by the actuator140 under the control of the controller 150. This causes the radiationbeam 120 to be swept from one side of the optical fiber to the other. Ina specific example of implementation, the radiation beam 120 is swept ata frequency of approximately 5 to 50 Hz, but other suitable sweepfrequencies can be used, depending on the exact type of fiber usedwithout detracting from the spirit of the invention. The radiation beam120 is swept continually in order to illuminate only briefly the core205 at each sweep. This brief illumination is preferable because mostcurrently available core materials present photoluminescence whichreduces in intensity when the radiation causing the photoluminescenceilluminates constantly a given portion of the core 205.

[0046] While the mirror 160 oscillates, the controller 150 stores in thememory intensity values for the photoluminescence conveyed by theintensity signal. The controller also stores in the memory a value ofthe angle at which the mirror 160 is positioned each time an intensityvalue is stored. In a first example of implementation, the value of theangle is determined by the controller 150 according to the controlsignals sent to the actuator 140. Therefore, in this example ofimplementation, there is an implicit assumption that the actuator 140positions the mirror 160 at angle values contained in the controlsignals. Alternatively, the angle values can be measured independentlyand fed to the controller 150.

[0047] After a variable number of sweeps, which depends on the requiredprecision in the alignment and on the uncertainties present in thestored angle values and intensity signal values, the controller 150 usesthe angle values and the intensity signal values stored in the memory tofind the optimal angle for the mirror 160. In a specific example ofimplementation, the optimal angle is an angle for which the measuredintensity value is maximal. Methods to determine the optimal angle arewell known in the art and will therefore not be described in furtherdetails. Finally, the mirror is angled at the optimal angle.

[0048] In a variant, the mirror is not rotatably mounted on the axle 155but is instead translatably mounted on a suitable actuator. In thisvariant, the translation of the mirror sweeps the beam 120 back andforth across the optical fiber 110. Alternatively, the optical fiber 110can be supported by a mobile fiber support 130. Then, the fiber support130 is swept back and forth across an immobile laser beam. The readerskilled in the art will readily recognize other possible implementationsthat do not depart from the spirit of the invention.

[0049] In a further variant, the laser beam 120 is not swept rapidlyenough across the optical fiber for the natural decay of thephotoluminescence in time to be negligible. However, the decay of thephotoluminescence in the core 205 can be modeled by the controller 205to correct the stored intensity values by generating adapted intensityvalues, thereby allowing the optimal angle to be determined as describedabove. The adapted intensity values take into account a natural decay ofphotoluminescence in time.

[0050] While the alignment procedure described above has been presentedin the context of an initial alignment prior to performing a process onthe optical fiber 110, the reader skilled in the art will appreciatethat the method could also be used periodically while the process isperformed to maintain the alignment of the optical fiber 110 with theradiation beam 120.

[0051] Although various embodiments have been illustrated, this was forthe purpose of describing, but not limiting, the invention. Variousmodifications will become apparent to those skilled in the art and arewithin the scope of this invention, which is defined more particularlyby the attached claims.

1. An apparatus for aligning an optical waveguide with a radiationsource, the waveguide having a longitudinal axis that defines a mainoptical propagation path, the radiation source illuminating thewaveguide such that the waveguide generates light via photoluminescence,at least a portion of the light generated via photoluminescence beingemitted from the waveguide along a direction generally transverse to thelongitudinal axis, said apparatus comprising: a) a sensor responsive tothe light emitted from the waveguide along a direction generallytransverse to the longitudinal axis for producing an output signal; b)alignment means to vary the alignment of the radiation source and thewaveguide at least partly in dependence of the output signal.
 2. Anapparatus as defined in claim 1, wherein said output signal is anintensity signal indicative of an intensity of light.
 3. An apparatus asdefined in claim 2, wherein said alignment means includes a controllermodule responsive to the intensity signal for causing the alignment ofthe radiation source and the waveguide to be varied.
 4. An apparatus asdefined in claim 3, where said controller module causes the radiationsource to be displaced in order to cause the alignment of the radiationsource and the waveguide to be varied.
 5. An apparatus as defined inclaim 3, where said controller module causes the waveguide to bedisplaced in order to cause the alignment of the radiation source andthe waveguide to be varied.
 6. An apparatus as defined in claim 4, wheresaid alignment means further comprise a light reflecting memberpositioned such as to redirect a radiation beam emitted by the radiationsource, said controller module being operative to cause said lightreflecting member to be displaced in order to cause the alignment of theradiation source and the waveguide to be varied.
 7. An apparatus asdefined in claim 6, wherein said light reflecting member is displaced bytranslation.
 8. An apparatus as defined in claim 6, wherein said lightreflecting member is displaced by rotation.
 9. An apparatus as definedin claim 6, wherein said light reflecting member includes a mirror. 10.An apparatus as defined in claim 6, wherein said controller modulegenerates a control signal at least in part on the basis of theintensity signal, said alignment means further including a actuatoroperatively coupled to said light reflecting member, said actuator beingresponsive to the control signal generated by said controller module fordisplacing said light reflecting member such as to vary the alignment ofthe radiation source and the waveguide at least in part on the basis ofthe control signal.
 11. An apparatus as defined in claim 10, whereindisplacing said light reflecting member includes a rotation of the lightreflecting member.
 12. An apparatus as defined in claim 10, whereindisplacing said light reflecting member includes a translation of thelight reflecting member.
 13. A method for aligning an optical waveguidewith a radiation source, the waveguide having a longitudinal axis thatdefines a main optical propagation path, said method comprising: a)illuminating the waveguide such that the waveguide generates light viaphotoluminescence, at least a portion of the light generated viaphotoluminescence being emitted from the waveguide along a directiongenerally transverse to the longitudinal axis; b) generating an outputsignal at least in part on the basis of light emitted from the waveguidealong a direction generally transverse to the longitudinal axis; c)varying the alignment of the radiation source and the waveguide at leastpartly in dependence of the output signal.
 14. A method as defined inclaim 13, wherein said output signal is an intensity signal indicativeof an intensity of light.
 15. A method as defined in claim 14,comprising displacing the radiation source in order to cause thealignment of the radiation source and the waveguide to be varied.
 16. Amethod as defined in claim 14, comprising displacing the waveguide inorder to cause the alignment of the radiation source and the waveguideto be varied.
 17. An apparatus suitable for aligning an opticalwaveguide with a radiation source, said apparatus comprising: a) awaveguide support member suitable for holding an optical waveguide, thewaveguide having a longitudinal axis that defines a main opticalpropagation path, the radiation source illuminating the waveguide suchthat the waveguide generates light via photoluminescence, at least aportion of the light generated via photoluminescence being emitted fromthe waveguide along a direction generally transverse to the longitudinalaxis; b) a sensor for positioning in proximity to the optical waveguide,said sensor being responsive to the light emitted from the waveguidealong a direction generally transverse to the longitudinal axis toproduce an intensity signal indicative of a measure of the lightdetected; c) a controller module responsive to the intensity signal forcausing the alignment of the radiation source and the waveguide to bevaried at least partly in dependence of the intensity signal.
 18. Anapparatus as defined in claim 17, where said waveguide support member ismoveable and the controller module is responsive to the intensity signalfor causing the waveguide support member to be displaced such as tocause the alignment of the radiation source and the waveguide to bevaried.
 19. An apparatus as defined in claim 17, where said controllermodule is responsive to the intensity signal for causing the directionof the radiation beam emitted by the radiation source to be altered suchthat the alignment of the radiation source and the waveguide to bevaried.
 20. An apparatus as defined in claim 17, wherein said sensor ismounted on said waveguide support member.
 21. An apparatus as defined inclaim 17, wherein the light detected by said sensor includes visiblelight.
 22. An apparatus as defined in claim 19 wherein said controlleris adapted to: a) process the intensity signal to generate an adaptedintensity signal, the adapted intensity signal taking into account anatural decay of photoluminescence in time; b) cause the alignment ofthe radiation source and the waveguide to be varied at least in part onthe basis of the adapted intensity signal.
 23. An apparatus as definedin claim 17, where said optical waveguide is an optical fiber.
 24. Anapparatus as defined in claim 17, where said optical waveguide isselected from the set consisting of optical fibers pre-assembled on amodule or waveguides manufactured through integrated optics processes.25. An apparatus suitable for aligning an optical waveguide with aradiation source, said apparatus comprising: a) support means forholding an optical waveguide, the waveguide having a longitudinal axisthat defines a main optical propagation path, the radiation sourceilluminating the waveguide such that the waveguide generates light viaphotoluminescence, at least a portion of the light generated viaphotoluminescence being emitted from the waveguide along a directiongenerally transverse to the longitudinal axis; b) sensor meansresponsive to the light emitted from the waveguide along a directiongenerally transverse to the longitudinal axis to produce an intensitysignal indicative of a measure of the light detected; c) control meansresponsive to the intensity signal for causing the alignment of theradiation source and the waveguide to be varied at least partly independence of the intensity signal.